Hot-gas piston engine

ABSTRACT

The invention relates to a hot-gas piston engine comprising at least one compression space of variable volume and at least one expansion space also of variable volume communicating with the former, said spaces having, in operation, relatively different temperatures, the volumes of these spaces being variable by means of piston-like bodies, which are connected each via a piston rod with a driving gear, whilst at least the piston-like body adapted to vary the volume of the expansion space is formed by a base element secured to the end of the piston rod concerned, said base element being provided on its side facing the expansion space with a heat-insulating piston cap.

United States Patent [1 1 DeLigny et al.

HOT-GAS PISTON ENGINE lnventors: Johan Herman DeWilde DeLigny;

Cornelis Leendert DeWit; Petrus Johannes Cornelius Van Rooii, all ofEmmasingel, Eindhoven, Netherlands U.S. Philips Corporation, New York,NY.

Filed: May 24, 1972 Appl. No.: 256,486

Related us; Application Data Continuation of Ser.' No. 119,577, March 1,1971, abandoned.

[73] Assignee:

[30] Foreign Application Priority Data Mar. 28, 1970 Netherlands 7004499[52] US. Cl 60/24, 92/128, 92/258, 92/259 Int. Cl. F02g 1/04 Field ofSearch 92/128, 181, 258, 92/259; 60/24 Primary Examiner-Martin P.Schwadron Assistant Examiner--Allen M. Ostrager Attorney-Frank R.Trifari' [5 7] ABSTRACT The invention relates to a hot-gas piston enginecomprising at least one compression space of variable volume and atleast one expansion space also of variable volume communicating'with theformer, said spaces having, in operation, relatively differenttemperatures, the volumes of these spaces being variable by means ofpistons bodies, which are connected each via a piston rod with a drivinggear, while at least the piston adapted to vary the volume of theexpansion. space is formed by a base element secured to the end of thepiston rod concerned, said base element *being provided on its sidefacing the expansion space with a heat-insulating piston cap.

1 Claim, 2 Drawing Figures PAIENTEU 3,783,612

WI 1 BF 2 Figfla IXK'ENTORS JOHAN H. DE WILDE DE LIGNY CORNELIS L. DEWIT PETRUS J.C. VAN ROOIJ Ari-1 PArtmwm 8M 3,783,612

sum 2 (IF 2 I N VENTURE,

JOHAN H DE WILDE DE LIGNY E WIT CORNELIS L D PETRUS J.C. VAN ROO'JAcid/7* HOT-GAS PISTON ENGINE This is a continuation, of applicationSer. No. 119,577, filed 3/1/71 now abandoned.

Hot-gas piston engines of the kind set forth, which are to be understoodto mean cold-gas refrigerators, hot-gas engines, cold-gas engines andheat pumps, are known. In order to avoid loss of heat or cold from theexpansion space the piston varying the volume'thereof in these enginesis formed by a base element secured to the piston rod concerned and ahollow or solid heatinsulating cap arranged on said element. This pistoncap provides a largeaxial dimension of the piston-like body.

The connection hitherto used between said pistonlike body and the pistonrod often gives rise to an inclined position of the piston-like bodyrelative to the rod, which results in jamming of the body in thecylinder due to said large axial dimension.

A further disadvantage of the conventional method of connection residesin that the nut fastening the piston-like body to the rod is locatedinside the assembly of the basic element and the piston cap so that indismounting and post-adjustment the piston cap has to be removed first.

The invention has for its object to provide a hot-gas piston engine ofthe kind set forth, in which said disadvantages are obviated.

The hot-gas piston engine according to the invention is for this purposecharacterized in that the base element is provided with a bore locatedon its centre line and fitting centrally around part of the piston rodconcerned, the side of the base element remote from the piston capengaging a face of the piston rod which is at right angles to the centreline of said piston rod, the latter being prolonged in the direction ofthe piston cap by a narrowed portion, which is provided with screwthreadat the ends for receiving a nut accommodated in a recess of the baseelement, the nut and the surrounding recess comprising two portions ofdifferent diameters, the parts of the larger diameter being located onthe side of the piston cap, whilst the gap-shaped space between theannular faces formed by the transitions of said parts, which space isotherwise closed, can be caused to communicate with a high-pressuremedium source through a communication channel passing through the baseelement and the side of the nut remote .from the piston cap is providedwith a plurality of radial slots distributed circumferentially andhaving depths decreasing inwardly in the radial direction, whilst thekey-shaped grooves formed by said slots and the side of the base elementfacing the piston cap accommodates' a fitting, key-shaped tighteningelement,- which is displaceable in a radial direction in the groove bymeans of a bolt held in a radial, tapped bore in the base element.

In the hot-gas piston engine embodying the invention the perpendicularposition is obtained by urging the base element against a face of thepiston rod at right angles to the centre line thereof. For this purposethe piston rod is first subjected to bias stress preferablyhydraulically by supplying the high-pressure medium to the gap betweenthe annular faces of the nut and the base element so that forces inopposite-directions are exerted on the nut and on the base element. Thenthe key-shaped tightening elements can be readily displaced inwardly tothe desired extent by tightening the bolts, after which, when thehigh-pressure medium is conducted away, the key-shaped tighteningelements continue urging away the nut from the base element so that thebase element remains urged against the piston rod in the desiredposition. Post-adjustment and dismounting can be carried out in a simplemanner without dismounting the piston cap by first subjecting the pistonrod to a higher bias stress with the aid of the high-pressure medium andby subsequently handling the bolts. An inclined position of the nut, ifany, is without consequence for the perpendicular position of thepiston.

A satisfactory centering is ensured by the cylindrical portion of thepiston rod located inside the bore of the base element.

The invention will be described more fully with reference to thedrawing, which shows by way of example, a hot-gas piston engine of thedisplacer type diagrammatically.

Referring to FIG. la reference numeral 1 designates a cylinder in whicha piston 2 and a displacer 3 are adapted to move. The piston 2 and thedisplacer 3 are connected by a piston rod 4 and a displacer rod 14 witha driving gear (not shown). Between the piston 2 and the displacer 3 thecompression space 5 communicates through a cooler 6, a regenerator 7 anda heater 8 with an expansion space 9 above the displacer. A burner (notshown) is provided for the supply of heat to the expansion space 9.

The displacer 3 comprises a base element 11 and a solid displacer 12 ofquartz or another material of poor thermal conductivity fastened to theformer.

The base element 11 has a bore 13 adapted to receive the 'end 15 of thedisplacer rod 14. The end 15 has a face 16 at right angles to the centreline of the displacer rod 14 and a cylindrical fitting face 17 nearlyheld in the bore 13. In this way the perpendicular position and thecentral position of the displacer is ensured by two separate faces. Theend 15 has furthermore a screwthreaded portion, on which a nut 18 isscrewed, which is held in a recess of the base element between theannular faces 19 and 20 of the nut 18 and the base element 11respectively a gap-shaped space 21 is left, which can be caused tocommunicate through a communication channel 22 with a pressurized oilsource. The space 21 is sealed by stuffing rings 23. With respect to thebase element 11 the nut 18 is fixed in position by means of a pin 30.Also from FIG. lb, a cross sectional view lb-Ib of FIG. 1a, it will beapparent that the nut 18 is provided on the lower side with three radialslots 25 at angles of between each other, the depths of which decreasetowards the piston'rod in a radial direction.

Together with the wall 26 of the base element 11 the slots 25 formkey-shaped grooves accommodating keyshaped tightening elements 27, whichare displaceable in'a radial direction in the wedge-shaped grooves bymeans of bolts 28 held in radial, tapped bores 29 in the base element11. By supplying pressurized oil via the communication channel 22' tothe gap-shaped space 21 the nut 18 and the base element 11 are urgedaway from each other by the oil pressure exerted on the annular faces 19and 20 so that the rod connection is subjected to preliminary stress. Bytightening the bolts 28 the key-shaped tightening elements 27 can now bereadily displaced inwardly over the desired distance. By eliminating theoil pressure'in'conducting the oil out of the space 21 the key-shapedtightening elements 27 ensure that the rod connection is maintained atthe desired bias stress. If the bolts are tightened unequally, there areno consequences for the perpendicular position of the displacer relativeto the displacer rod. A post-adjustment, if desired, may be carried outin a simple manner by supplying pressurized oil to the space 21, bysubsequently tightening the bolts 28 to the desired extent and byreconducting away the pressurized oil. This connection has the advantagethat the displacer 3 can be rigidly connected with the displacer rod 14without the need for removing the displacer cap 12 from the base element1 l, which is even not possible in given structures because they arerigidly connected with each other.

The displacer 3 can be loosened from the displacer rod 14 by supplyingpressurized oil to the space 21, by subsequently loosening the bolts 28,so that the keyshaped tightening elements 27 are released and can bedisplaced outwardly, after which the oil pressure is eliminated and thedisplacer 3 is turned relatively to the displacer rod 14. Then the nut18 maintains its place relative to the base element 11 owing to the pin30 so the displacer rod 14 can be screwed out of the nut 18 without therisk of causing this nut to turn as well.

The seal between the displacer3 and the cylinder 1 is ensured by twopiston rings 31 and 32, each of which is provided at their distal sideswith radial grooves 33. These grooves ensure that in operation theminimum pressure of the operating space always prevails in the space 34between the piston rings3l and 32. By connecting the space 34 through achannel 35 with the space 36 between the displacer cap 12 and the baseelement 11, the minimum pressure will also prevail constantly in thespace 36, which means that the displacer cap 12 is constantly urgedpositively to the base element 11.

From the foregoing it will be obvious that the invention provides aninteresting and simply post-adjustable connection between the displacerand the displacer rod of a hot-gas piston engine, whilst post-adjustmentor release of this connection can be carried out with the need forremoving the displacer cap.

What is claimed is:

1. A hot-gas piston engine comprising at least one compression space ofvariable volume and at least one expansion space communicating with theformer and also having a variable volume, said spaces having inoperation relatively different temperatures, the voltimes of said spacesbeing variable by piston-like bodies, which are each coupled through apiston rod with a driving gear, in which at least the piston-like bodyadapted to vary the volume of the expansion space is formed by a baseelement connected with the end of the piston rod concerned, said baseelement being provided on its side facing the expansion space with aheatinsulating piston cap, characterized in that the base element isprovided with a central bore fitting centrally around part of the pistonrod concerned, the side of the base element remote from the piston capengaging a face of the piston rod at right angles to the centre line ofsaid rod, the piston rod being prolonged in the direction of the pistoncap by a narrowed portion which is provided with screwthread at the end,which receives a nut accommodated in a recess of the base element, thenut and the surrounding recess comprising two portions of difierentdiameters, the portions of the larger diameters being located on theside of the piston cap, whilst the otherwise sealed gap-shaped spacebetween the annular faces formed by the transitions of said por tionscan be caused to communicate with a highpressure medium source through aconnecting channel passing through the base element and the side of thenut remote from the piston cap is provided with a plurality of radialslots distributed along the circumference and having depths decreasinginwardly in a radial direc tion, each of the key-shaped grooves formedby said slots and the side of the base element facing the piston capaccommodating an associated key-shaped tightening element, which isdisplaceable in the groove in the radial direction by means of a boltheld in a radial,

tapped bore of the base element.

1. A hot-gas piston engine comprising at least one compression space ofvariable volume and at least one expansion space communicating with theformer and also having a variable volume, said spaces having inoperation relatively different temperatures, the volumes of said spacesbeing variable by piston-like bodies, which are each coupled through apiston rod with a driving gear, in which at least the piston-like bodyadapted to vary the volume of the expansion space is formed by a baseelement connected with the end of the piston rod concerned, said baseelement being provided on its side facing the expansion space with aheat-insulating piston cap, characterized in that the base element isprovided with a central bore fitting centrally around part of the pistonrod concerned, the side of the base element remote from the piston capengaging a face of the piston rod at right angles to the centre line ofsaid rod, the piston rod being prolonged in the direction of the pistoncap by a narrowed portion which is provided with screwthread at the end,which receives a nut accommodated in a recess of the base element, thenut and the surrounding recess comprising two portions of differentdiameters, the portions of the larger diameters being located on theside of the piston cap, whilst the otherwise sealed gap-shaped spacebetween the annular faces formed by the transitions of said portions canbe caused to communicate with a high-pressure medium source through aconnecting channel passing through the base element and the side of thenut remote from the piston cap is provided with a plurality of radialslots Distributed along the circumference and having depths decreasinginwardly in a radial direction, each of the key-shaped grooves formed bysaid slots and the side of the base element facing the piston capaccommodating an associated key-shaped tightening element, which isdisplaceable in the groove in the radial direction by means of a boltheld in a radial, tapped bore of the base element.